Method and apparatus for continuous flow analysis of liquid sample

ABSTRACT

A continuous flow analyzer of the type which introduces continuously a carrier liquid into a single tubular conduit to form a stable main carrier stream and injects predetermined volumes of reagent liquid and sample liquid in series into the main carrier stream. The analyzer reduces the consumption of the reagent and can form a stable continuous flow.

This is a division of application Ser. No. 442,671, filed Nov. 18, 1982,now U.S. Pat. No. 4,520,108.

BACKGROUND OF THE INVENTION

This invention relates to a continuous flow system automatic analyzingmethod and apparatus. More particularly, the present invention relatesto an automatic analyzing method and apparatus which consumes a reducedquantity of a reagent and has high reliability.

Continuous flow analysis comprises forming a continuous flow of areagent or a carrier solution, charging a sample into the continuousflow and guiding the flow to a detector for measurement. This analysishas gained a wide application in automatic analyzers because it providesthe advantages that the measuring time can be shortened, not only thereaction result but also the reaction process can be measured and only atrace amount of sample is necessary. An example of the continuous flowanalyzer of the prior art is disclosed in U.S. Pat. No. 4,022,575, forexample. In accordance with this prior art, a carrier stream is formedby a reagent and a necessary amount of sample is charged into thestream. Though this method has the large advantage that the constructionis simple, it is not free from the disadvantage that the reagent must beconstantly caused to flow and hence, a large amount of reagent isnecessary. In addition, the liquid pressure and flow velocity in theflow path must be accurate and stable because the time from introductionof the sample till measurement and the time required for the sample topass through the reaction portion significantly affect the measuringaccuracy. Accordingly, a waiting time is necessary from the start ofoperation of a pump till the start of analysis so as to stabilize theflow and the reagent is consumed in vain in the interim. If theanalyzing method is changed, large quantities of reagent must also becaused to flow in order to replace the reagents.

British Laid-Open Pat. No. 2,023,286 discloses an apparatus as animprovement over the conventional continuous flow analyzer of the kinddescribed above. In this improved apparatus, two carrier flow paths aredisposed and one is used as a sample introduction path with the other,as a reagent introduction path. Both flow paths are joined together onthe downstream side into a single flow path and the reagent and thesample are guided to the reaction portion. Accordingly, the carrierliquid is always caused to flow through the path and the condition ofthe path is kept stable. The reagent in a necessary amount is introducedin synchronism with the introduction of the sample only at the time ofanalysis so that the reagent can be saved. In addition, the reagents canbe easily replaced when the analyzing method is changed.

However, the drawback of this improved apparatus is that since twocarrier flow paths are disposed, two liquid feed pumps must be disposedand the overall size of the apparatus becomes great. In this apparatus,the performance of the pumps affect significantly the accuracy ofanalysis so that high precision pumps must be employed, resultingeventually in the increase of the cost of production. Hence, the numberof pumps is preferably as small as possible.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide acontinuous flow system analyzer which has high accuracy of analysis andhigh reliability.

It is another object of the present invention to provide a continuousflow system analyzer which is simple in construction and yet has astable carrier stream.

It is still another object of the present invention to provide acontinuous flow system analyzer which can charge both reagent and sampleinto a carrier stream or into a reaction portion at a suitable timing.

It is a further object of the present invention to provide a continuousflow system analyzer which consumes only a reduced quantity of reagent.

The present invention is characterized in that a carrier liquid iscaused to continuously flow into a single tubular conduit to form acontinuous carrier stream and predetermined volumes of reagent andsample are charged into the carrier stream either in series or in thestate in which the sample is interposed between the reagent.

These and other objects and features of the present invention willbecome more apparent from the following detailed description as well asfrom the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B diagrammatically illustrate the construction of thecontinuous flow system analyzer in accordance with one embodiment of thepresent invention;

FIGS. 2A and 2B diagrammatically illustrate the construction of thecontinuous flow system analyzer in accordance with another embodiment ofthe present invention;

FIG. 3 diagrammatically illustrates the construction of a rotary valveused in the embodiments of the present invention; and

FIGS. 4A and 4B are partial sectional views useful for explaining thechange-over operation of the rotary valve shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one embodiment of the present invention shown in FIG. 1A, a reactionportion 20 and a detector 30 are connected to a main carrier conduit 10through which the carrier liquid is caused to flow continuously. Areagent conduit 40 and a sample conduit 50 are connected to the maincarrier conduit 10 via a rotary valve 60 and are selectively connectedand disconnected to and from the main conduit by the operation of therotary valve 60.

A peristaltic pump is used as the carrier liquid pump 12 and feeds at aconstant flow velocity the carrier liquid (distilled water) from acarrier liquid container 14 to the reaction portion 20 and to thedetector 30 through the main carrier conduit 10, forming a stablecarrier stream. A reaction coil 16 is disposed in the reaction portion20.

One end of the reagent conduit 40 is connected to a pump 80 via a firstreagent metering pipe 46, a second reagent metering pipe 48 andchange-over valve 70 that are connected to the rotary valve 60. Areagent probe 44 is connected to the other end of the reagent conduit 40and sucks the reagent liquid from the reagent container 42. Similarly,one end of the sample conduit 50 is connected to the pump 80 via asample metering pipe 56 and the change-over valve 70 that are connectedto the rotary valve 60. A sample probe 54 is connected to the other endof the sample conduit 50 and sucks the sample from a sample container52. In the state shown in the drawing, the change-over valve 70 connectsthe pump 80 to the sample flow system and introduces the sample from thesample container 52 into the sample metering pipe 56. Next, thechange-over valve 70 is changed over to the reagent flow system andintroduces the reagent liquid from the reagent container 42 into thereagent metering pipes 46, 48.

In the state shown in FIG. 1A, the main conduit 10 is cut off from thereagent flow system 40 and from the sample flow system by the rotaryvalve 60. Each of the reagent metering pipes 46, 48 and the samplemetering pipe 56 has an inner diameter and length so that its volumecoincides with the volumes of reagent and sample necessary for theanalysis. According to this arrangement, the accurate and necessaryvolumes of reagent and sample for the analysis are introduced into therespective pipes upon the operation described above.

After the reagent and the samples are introduced into the respectivepipes in the manner described above, the rotary valve 60 rotates andforms the flow path shown in FIG. 1B. In the drawing, one end of thereagent matering pipe 46 filled with the reagent liquid is connected toone end of the sample metering pipe 56 filled with the sample liquid andthe other end of the sample metering pipe 56 is connected to one end ofanother reagent metering pipe 48. Accordingly, the sample liquid in thesample metering pipe 56 comes into contact in series with, andinterposed by, the reagent in the two reagent metering pipes 46 and 48.The other end each of the reagent metering pipes 46, 48 is connected tothe main conduit 10 filled with the carrier liquid. In other words, aflow path is defined in which the sample liquid, which is interposedbetween the reagent liquid, is introduced into the carrier stream. Whenthe carrier pump 12 is operated under this state, the sample liquid issupplied to the reaction coil 16 while being interposed between thereagent liquid. During the period in which the sample liquid introducedinto the main carrier stream passes through the reaction coil 16, itundergoes the reaction with the reagent and measurement is effected bythe detector 30.

The embodiment described above employs the system in which two reagentmetering pipes are disposed so as to introduce the sample into the maincarrier stream while the sample is being interposed between the reagentliquid, but either of the reagent pipes may be deleted. In short, it isonly necessary that the sample liquid be introduced into the maincarrier stream while it keeps contact with the reagent liquid. If bothreagent metering pipe and sample metering pipe are detachable, themetering pipes having different capacities can be fitted in accordancewith the sample and reagent in the volumes necessary for the analysis,thus making it possible to make the continuous flow system moreconvenient.

In this embodiment, measurement can be carried out using the minimalnecessary volumes of sample and reagent. The detection accuracy of thereaction condition can be also improved because the sample is introducedin series while being interposed between the reagent liquid and thestable flow path is constantly formed by the carrier stream.

FIG. 2A shows another embodiment of the present invention, in which likereference numerals are used to identify like constituents as in FIG. 1A.The basic construction of this embodiment is the same as the foregoingembodiment shown in FIG. 1A. The main carrier stream is formed in themain carrier conduit 10. In this embodiment, the separate rotary valvesand pumps are used for the reagent liquid and for the sample liquid,respectively. As shown in the drawing, the rotary valve 62 and pump 82for the reagent are connected to the reagent conduit 40, and the rotaryvalve 64 and pump 84 for the sample are likewise connected to the sampleconduit 50. The rotary valves 62 and 64 can be interconnected to eachother while the rotary valve 62 can be interconnected to the maincarrier conduit 10. Under the state shown in FIG. 2A, the stable carrierstream is formed as the main carrier conduit 10 is cut off from bothreagent flow system and sample flow system.

On the other hand, the reagent rotary valve 62 is also cut off from thesample flow path so that the carrier stream, the reagent flow system andthe sample flow system form the independent flow systems, respectively.The reagent liquid in the reagent container 42 enters the reagent pump82 and is introduced into and metered by the reagent metering pipes 46,48. The sample in the sample container 52 is introduced into and meteredby the sample metering pipe 56.

Thereafter, the rotary valves 62 and 64 are rotated to change the stateof interconnection as shown in FIG. 2B. In the drawing, one end each ofthe reagent metering pipes 46, 48 of the reagent rotary valve 62 isconnected to the sample metering pipe 56 of the rotary valve 64 so thatthe sample liquid is interposed in series between the reagent liquid. Onthe other hand, the other end each of the reagent metering pipes 46, 48is inserted into and connected to the main carrier conduit 10.Accordingly, the sample that is interposed between the reagent liquid isintroduced in series into the main carrier stream. In this embodiment,the mixer 18 is connected to the main carrier conduit and mixes thesample with the reagent. This embodiment provides the same effect as theforegoing embodiment shown in FIG. 1A. Additionally, this embodimentmakes it possible to simplify the construction of each rotary valve anda common driving source can be used in common for both rotary valvesbecause they can be changed over simultaneously. Though this embodimentuses two pumps, the performance of the pumps 82, 84 does not affect theaccuracy of analysis because metering of the reagent and sample iseffected by the respective metering pipes and introduction of the sampleand reagent into the main carrier stream is carried out by the rotaryvalve and the carrier pump 12. Hence, economical pumps can be employed.

The rotary valve to be used in the embodiments shown in FIGS. 1A and 2Amay have a known, commercially available construction. An example of theconstruction is shown in FIGS. 3 and 4.

FIG. 3 is a schematic view showing the appearance of the rotary valve.The rotary valve 60 consists of a rotary portion 61 and a fixed portion63 and is constructed so that slide surfaces 65 and 66 slide whilekeeping contact with each other under the air-tight state. Change-overholes A through F are bored on the slide surface 66 of the fixed portion63 and communicate with passages A' through F', respectively. Grooveholes G, H and J are defined on the slide surface 65 of the rotaryportion 61. Connection of the passages is shown in FIGS. 4A and 4B.Referring to FIG. 4A, when the sample is introduced from the passage A'into F', the passages B' through F' serve as the sample metering pipesand the volume of the sample is determined by this length. The passagesC', D' are for introducing the sample into the main carrier conduit, forexample and the carrier liquid or the reagent liquid is caused to flowin this case. When the rotary portion 61 is rotated under this state andthe state of connection is changed over as shown in FIG. 4B, the meteredsample is connected to the passages C', D' and is introduced into themain carrier stream.

In both of the embodiments shown in FIGS. 1 and 2, after the sample andthe reagent are introduced into the main carrier conduit, thechange-over valve is changed over so as to cut them off from the maincarrier conduit and the change-over valve can suck and meter thesubsequent sample and reagent during the period in which analysis iscarried out in the main carrier conduit. Accordingly, the next samplecan be introduced immediately after completion of analysis of theprevious sample. Moreover, even before the analysis of the previoussample is not yet completed, the sample can be introduced sequentiallywith such an interval in which the previous sample does not overlap withthe next sample. The method of analysis can be easily changed over byreplacing the reagent container by the reagent container for anotheranalytical method.

As described in the foregoing, the present invention makes it possibleto reduce consumption of the reagent and to improve the reliability.

What is claimed is:
 1. An apparatus for flow analysis of a liquidsample, comprising: means for introducing a carrier liquid into a mainsingle tubular conduit to form a carrier stream; a reagent metering pipehaving a predetermined capacity; means for introducing a reagent liquidinto the reagent metering pipe; a sample metering pipe having apredetermined capacity; means for introducing a sample liquid into thesample metering pipe; means for connecting the reagent metering pipe andthe sample metering pipe with each other in series and for connectingthe main conduit with the reagent metering pipe and the sample meteringpipe so that the reagent liquid from the reagent metering pipe and thesample liquid from the sample metering pipe can be carried in seriesinto the main conduit by directing the carrier liquid from said mainconduit into the reagent metering pipe and the sample metering pipe;means for reacting said sample liquid with said reagent liquid; andmeans for detecting a reaction condition of said sample liquid with saidreagent liquid.
 2. An apparatus for flow analysis of a liquid sample,comprising: a main single tubular conduit; means for introducing acarrier liquid into the main single tubular conduit to form a carrierstream; first and second reagent metering pipes having a predeterminedcapacity, each of said first and second metering pipes having first andsecond ends; means for introducing a reagent liquid into the first andsecond reagent metering pipes; a sample metering pipe having apredetermined capacity; means for introducing a sample liquid into thesample metering pipe; means for connecting the sample metering pipebetween the first ends of each of the first and second reagent meteringpipes so that the first reagent metering pipe, the sample metering pipeand the second reagent metering pipe are in series, and for connectingthe second end of each of the first and second reagent pipes with themain conduit; means for reacting said sample liquid with said reagentliquid; and means for detecting a reaction condition of said sampleliquid with said reagent liquid.
 3. An apparatus for flow analysis of aliquid sample comprising: a first pipe means for metering a liquidsample of a predetermined volume; means for introducing the liquidsample into the first pipe means; second pipe means for metering areagent solution of a predetermined volume; means for introducing thereagent solution into the second pipe means; a reaction zone to reactthe sample with the reagent; a detection zone to detect the samplereacting with the reagent; a main conduit for forming a carrier streamof a carrier liquid; means for directing the carrier stream to thereaction zone and the detection zone; means for cutting off the firstpipe means from the main conduit when the sample is introduced into thefirst pipe means and for cutting off the second pipe means from the mainconduit when the reagent is introduced into the second pipe means; meansfor connecting the first and second pipe means in series; means forcommunicating the main conduit with the first and second pipe meansconnected in series for introducing the sample and the reagent into themain conduit in series by diverting the carrier stream so as to pass thecarrier stream through the first and second pipe means connected inseries.
 4. An apparatus for flow analysis of a liquid sample,comprising: a sample metering pipe having first and second ends; a firstreagent metering pipe having first and second ends; a second reagentmetering pipe having first and second ends; a reaction zone to react asample with a reagent; a detection zone to detect the sample reactedwith the reagent; a main conduit for carrying a carrier stream of acarrier liquid; means for directing the carrier stream to the reactionzone and the detection zone; and means for connecting the first end ofthe sample metering pipe with the first end of the first reagentmetering pipe, for connecting the second end of the sample metering pipewith the first end of the second reagent metering pipe, and forconnecting the second ends of each of the first and second reagentmetering pipes with the main conduit, so that the carrier stream may bepassed through the first reagent metering pipe, the sample metering pipeand the second reagent metering pipe.
 5. An apparatus for flow analysisof a liquid sample, comprising: detecting means for detecting a reactioncondition of a sample liquid with a reagent liquid; a main conduit forforming a carrier stream of a carrier liquid; means for directing thecarrier liquid in the main conduit toward the detecting means; a singlemetering pipe, having first and second ends, for the introduction of asample liquid therein; two reagent metering pipes, each having first andsecond ends, for the introduction of the reagent liquid therein; valvemeans for connecting the first end of the sample metering pipe to thefirst end of one of the reagent metering pipes, for connecting thesecond end of the sample metering pipe to the first end of the otherreagent metering pipe, for connecting the second ends of each of the tworeagent metering pipes to the main conduit, for cutting off the samplemetering pipe from the main conduit and for cutting off the two reagentmetering pipes from the main conduit; means for introducing the sampleliquid into the sample metering pipe when the valve means cuts off thesample metering pipe from the main conduit; and means for introducingthe reagent solution into the two reagent metering pipes when the valvemeans cuts off the two reagent metering pipes from the main conduit. 6.An apparatus according to claim 5, wherein said valve means comprises arotary valve.
 7. An apparatus for flow analysis of a liquid sample,comprising: means for detecting a reaction condition of a sample liquidwith a reagent liquid; a main conduit for forming a carrier stream of acarrier liquid; means for directing the carrier liquid in the mainconduit toward the detecting means; a single sample metering pipe,having first and second ends, for the introduction of the sample liquidtherein; two reagent metering pipes, each having first and second ends,for the introduction of the reagent liquid therein; a first connectingmeans selectively connected to the main conduit and a second connectingmeans selectively connected to the sample metering pipe; wherein thefirst end of each of the two reagent metering pipes is connected to thefirst connecting means, the second end of each of the two reagentmetering pipes is connected to the second connecting means and the firstand second ends of the sample metering pipe are connected to the secondconnecting means; the first and second connecting means each having twooperative positions, one of the operative positions allowing the mainconduit, the two reagent metering pipes and the sample metering pipe tobe independent of one another and the second operative position allowingthe main conduit, the two reagent metering pipes and the sample meteringpipe to be connected in series.
 8. An apparatus according to claim 7,wherein said first and second connecting means comprise rotary valvemeans.